This invention is generally related to blowers or fans such as those used adjacent to a heat exchanger or in forced-air heating.
Gray U.S. Pat. No. 4,358,245 discloses a fan with highly forwardly skewed blades that generate less noise than comparable radial (straight) blades.
Gray U.S. Pat. No. 4,569,632 discloses a fan with rearwardly skewed blades which also exhibit less noise. To compensate for the rearward skew, the blade pitch decreases with increasing radius.
Gray U.S. Pat. No. 4,569,631 discloses a fan which has a highly forwardly skewed (leading edge skew) blades at the tip (where velocity and therefore noise are highest). The fan exhibits good strength due to an initial rearward blade skew at the root, which results in a relatively low overall (root-to-tip) offset.
Pezeshkzad, EP 0,168,594 discloses a fan with a blade chord that increases as a function of radius over the outer 80% of the blade and a blade thickness which increases as a function of radius over the outer 30% of the blade.
Perosuro U.S. Pat. No. 4,684,324 discloses a fan with blades having a high forward skew at the tip and an initial rearward skew toward the blade root.